1. Field of the Invention
The present invention relates to a substitute ground material and to a process for making such material, and to a ground treatment method. In another aspect, the present invention relates to a substitute ground material comprising sand, clay or silt and a polymer/oil binder, to a process for making such a substitute ground surface material, and to a method of treating an existing dirt track. In yet another aspect, the present invention relates to a substitute ground material comprising sand, clay or silt and an interpolymer/oil binder, to a process for making such a substitute ground surface material, and to a method of treating an existing dirt track by applying an aqueous emulsion of an interpolymer/oil binder to the dirt track.
2. Description of the Related Art
Dirt tracks utilized in horse racing generally comprise a mixture of sand, clay and silt and generally include a top layer "cushion" that overlays "pad" that are both supported on a suitable "substrate" or "base".
The base is consolidated matter upon which the pad and the cushion are layered. The pad is generally a layer of dirt on the order of about four to about twelve inches thick, that is laid upon the base and compacted to a bulk density of about 1.7. The cushion is generally on the order of about three inches thick and comprises loose, fluffy rakable material with a bulk density of about 1, and may be laid upon the pad, or cut from the pad by raking. In the care and maintenance of the dirt racetrack, the cushion is generally "worked" with a harrow, while the pad remains compacted and is occasionally disturbed.
Ideally, the dirt track must provide proper shock absorbency and adequate traction for the running of a safe race.
It has been suggested in the prior art that proper dirt track maintenance requires a good harrowing program to break up the cushion dirt compacted by horse's hooves and to maintain uniformity in the cushion's density and depth. Such a program requires proper harrowing equipment and proper frequency of harrowing.
It has been further suggested in the prior art that proper dirt track maintenance requires a proper moisture control program. Unfortunately, dirt tracks are very moisture sensitive and generally require a moisture content of about 7 to about 11 weight percent in the cushion for suitable track conditions. At a low moisture content, a dirt track tends to become dry and will, especially in a turn, tend to fall away from the horse's hooves. At a high moisture content, generally above 14 weight percent, the track tends to become "sloppy" at which point the watery track tends to squirt out from under the horse's hoof, giving the horse little or no support.
While it is understood that a dirt track requires seven to eleven weight percent moisture content, it is generally very difficult to keep the track within the desired operating range. Unfortunately, the ordinary water truck tends to increase moisture content by 0.3 percent per pass. Thus, on a very hot, dry day, where more than 0.3 percent water is being lost between passes of the water truck, a situation is encountered in which the water truck cannot keep up with evaporative losses.
Additionally, uniformity of the moisture content across the surface of the dirt track is generally impossible to achieve. Because of variances in shade, wind currents and other factors, evaporation rates can be dramatically different from place to place across the track.
In an effort to improve horse racetracks and overcome some of the deficiencies of dirt tracks, there have been alternative racetrack surfaces disclosed in the prior art which generally do not require constant watering to maintain a suitable moisture content.
For example, U.S. Pat. No. 4,792,133, issued Dec. 20, 1988 to Hawkins et al., discloses a substitute ground surface material suitable for use as the rakable "cushion" portion of a horse or dog race track. As disclosed, the substitute ground surface material comprises about 94 percent sand or a like material which is added to a polymeric binder comprising 10 percent polymeric material, such as ethylene vinyl acetate, polystyrene, nylon, polypropylene or polyvinyl chloride, dissolved in an oil that is generally a non-free flowing grease at normal track operating conditions. Typically, about six to about eight inches of the resulting coated substitute ground surface material, is then laid as a permanently rakeable cushion over a subsoil or suitable porous graded base. The surface of this cushion is maintained by raking or turning over the top two or three inches of the cushion.
U.S. Pat. No. 4,852,870, issued Aug. 1, 1989 to Hawkins et al., also discloses a substitute ground surface material suitable for use as the rakable "cushion" portion of a horse or dog race track. As disclosed, the substitute ground surface material comprises about 94 percent sand or a like material which is added to a binder comprising 10 percent styrene-butadiene-styrene copolymer dissolved in an oil that is generally non-free flowing grease at normal track operating conditions. Other disclosed polymers include polypropylene. The resulting coated substitute ground surface material, which is permanently capable of being raked, is then laid as a cushion layer over a subsoil or suitable porous graded base, with the the top of the cushion maintained by raking.
U.S. Pat. No. 4,968,024, issued Nov. 6, 1990 to Hawkins, discloses a substitute ground surface material suitable for use as the rakable "cushion" portion of a horse or dog race track. As disclosed, the substitute ground surface material comprises 98 percent sand or a like material which is added to binder comprising 20 to 40 percent styrene-butadiene-styrene copolymer dissolved in an aromatic oil that is generally free-flowing at normal track operating conditions. The resulting coated substitute ground surface material, which is permanently capable of being raked, is then laid as a cushion layer over a subsoil or suitable porous graded base, with the surface maintained by raking and light rolling.
EP 0 419 170 A3 published Mar. 27, 1991 discloses a substitute ground surface material suitable for use as the rakable "cushion" portion of a horse or dog race track. As disclosed, the substitute ground surface material comprises from 93.5 to 98 weight percent sand or a like material which is added to binder comprising 10 to 60 weight percent styrene-butadiene-styrene copolymer dissolved in an aromatic oil that is generally free-flowing at normal track operating conditions. The resulting coated substitute ground surface material, which is permanently capable of being raked, is then laid as a cushion layer over a subsoil or suitable porous graded base, with the top of the cushion maintained by raking.
The above references all disclose that the substitute material is laid upon the base as a six to eight inch permanently rakeable cushion layer, as opposed to the traditional method of forming a compacted pad layer upon the base and cutting a cushion from the compacted pad. In the actual use of the above substitute materials, the pad layer is generally formed by horses' hooves. Unfortunately, a pad formed from such a permanently rakable material will give a soft or mushy layer which is more suitable for use as a training track, i.e. such as the "trots" in England. Such an alternative surface is not suitable for use in American racetracks which generally require a harder compacted pad layer.
Additionally, the prior art alternative racetrack surfaces require the fabrication of a pad and/or cushion which is then laid upon a base. With existing dirt racetracks, this means that the existing cushion and any pad must first be removed from the base, and then the new pad fabricated and then laid upon the base. However, as there are numerous dirt tracks in existence, there is a need in the art for a method of treating existing dirt racetracks without having to remove the existing cushion and pad.